In short, yes!
In cats, we use the term ‘cat flu’ for respiratory infections in cats that cause signs similar to what you would expect in human flu. The situation in cats is more complex as signs can be caused by multiple pathogens, not just one virus as in the case of humans. 90% of cat flu cases are due to infection with either feline calicivirus (FCV), feline herpes virus (FHV or FHV-1), or both viruses together. Both the bacteria, Bordetella bronchiseptica and Chlamydophila felis, can also cause flu-like symptoms. A mish-mash of these organisms can occur, making this disease far from simple for vets and owners to understand.
How can my cat catch flu?
Cat flu is not infectious to people. Cats are infected via direct contact with infected cats, or their nasal discharge, tears or saliva in the environment. A cat’s sneeze droplets can travel several meters and the virus remains in the environment for up to 10 days. It can be carried around on clothing so indoor cats may be infected too. Cats kept in large groups such as breeding colonies, feral colonies or catteries and rescue centres are very susceptible as the virus spreads easily.
There is another route of infection making things more complex. Cats that survive herpes virus infection remain ‘carriers’ for life. Usually they show no signs of illness but shed the virus as above. Many don't shed enough virus to cause infection, but some will during times of stress. They may show mild signs such as runny eyes or sneezing but more often appear healthy. In this way, a healthy looking cat, stressed by the new arrival of another cat, may shed in enough volume to infect its new companion. It might be wrongly labelled a vaccine failure, or brought in by the new arrival. A cat that is having kittens may shed the virus, infecting her kittens at a very vulnerable time. Even a trip to the vet’s may induce shedding.
With FCV, most cats will also remain carriers, but usually only for weeks, or months, and most will eliminate the virus eventually.
What symptoms might I see?
Some signs of viral infection are similar to those that we expect with a cold or flu-like virus in humans and include:
● Nasal discharge.
● Sore and runny eyes.
● Lack of appetite.
Some infections are mild and may even go unnoticed. However, in very young, very old or immunosuppressed cats (due to medications or illnesses such as FeLV or FIV), the symptoms can be severe. Dehydration and lack of nutrition can cause cats to spiral downhill.
It is impossible to tell the two viruses apart just from signs. However FHV tends to be more severe and more commonly causes sore eyes (from corneal ulceration), a sore throat and a cough. FCV is often milder, with less of an effect on the eyes, but can cause mouth ulcers which lead to drooling. It also affects the joints in kittens, causing ‘kitten limping syndrome’. A more serious form of this virus called virulent systemic FCV (vs FCV) can occur, which may sadly be fatal - but is fortunately quite rare.
Secondary bacteria can contribute to the complexity of this disease. Bordetella bacteria (which can also cause kennel cough in dogs) often causes sneezing, a nasal discharge and coughing. Damage of the delicate nasal structure can result in a permanent runny or stuffy nose known as rhinitis. Chlamydophila usually causes eye problems (conjunctivitis), which can be very severe. Pneumonia can also be a very serious complication often due to secondary bacterial infection.
How is cat flu diagnosed?
Usually the signs lead to a diagnosis of cat flu. Swabs can be taken from the mouth to look for viruses. However this is rarely done given the limited treatments for viruses, thus the treatment is usually not changed by identifying which virus(es) is/are the culprits.
Is there anything I can do?
Yes! Simple nursing of poorly cats; making sure they are warm, bathing sore noses and eyes is very important. This may be done at home, or if very ill, in a hospital environment.
Using tasty, smelly foods, warmed gently may help stimulate the often poor appetite. Steam inhalation or nebulisers may help any nasal congestion which may help smell return, with appetite following. Very occasionally, tube feeding is needed. If dehydration is present, intravenous fluids are needed.
Although antibiotics do not treat viral infections, if the vet suspects a secondary bacterial infection, they are used.
Interferons are proteins made by the body in part to help fight viruses. Synthetic versions of these interferons are sometimes used as antivirals. There is only weak evidence for their effectiveness and they are expensive, so are rarely used. They may be of benefit if given early in the disease. There are antivirals to help treat FHV related eye disease, and the eye drops can be quite effective.
Can cat flu be prevented?
Yes. Widely available vaccines to the viral components are recommended for both indoor and outdoor cats. They usually prevent disease, although disease may still develop but in a much milder form. There is only one strain of FHV, but there are several strains of FCV so the vaccines may not be effective against all of them. Remember the FHV vaccine will be ineffective if your cat is already a carrier, which is very hard to tell. So even vaccinated cats can be carriers. Ideally, vaccinate new cats early and keep them separate until the vaccine is deemed effective. There are vaccines available for some of the bacterial causes, mainly useful for breeders, rescue homes, and cats attending cat shows, where there are a lot of cats together.
Ideally, keep any infected cats isolated with separate food, water and litter trays, and use 5% bleach to disinfect the area regularly (take care to rinse well as it is an irritant to cats). Be aware that although you can't catch these viruses you may carry the virus to other cats on your clothes and shoes etc.